ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Change in holding gain (loss) on securities available-for-sale [Abstract]
Change in net unrealized holding gain (loss) during the period	$ 4,611	$ (1,188)
Reclassification adjustment for net gains included in net gain on securities and other assets	76	(1,370)
Net change	4,687	(2,558)
Tax expense (benefit)	1,507	(850)
Net change in holding gain (loss) on securities available-for-sale	3,180	(1,708)
Change in pension and other postretirement obligations [Abstract]
Reclassification adjustment for expense included in other expense	122	286
Change in the net actuarial gain or loss	370	(131)
Net change	492	155
Tax expense	158	51
Net change in pension and other postretirement obligations	334	104
Change in gain (loss) on derivative assets [Abstract]
Change in net unrealized gain (loss) during the period	(2,928)	2,081
Reclassification adjustment for expense included in interest expense	(356)	(65)
Net change	(3,284)	2,016
Tax expense (benefit)	(1,038)	687
Net change in unrealized loss on derivative asset or liability	(2,246)	1,329
Other comprehensive income (loss), net of tax	$ 1,268	$ (275)